If you get an error in Eclipse Android development tool (on Windows), which says: Error generating final archive (Debug Certificate expired), it is happening because your debug.keystore has expired. Typically it's only good for 365 days. Anyhow, this is how you can fix the problem:

Go to: C:\user\yourname.android\ folder and delete the file called: debug.keystore Then open Eclipse: Go to Project, select Clean the project. Then close Eclipse and open it again. Go to: C:\user\yourname.android\ folder, you should now see a new debug.keystore file created. You should now be able to debug run your Android app again.